Detection system accuracy is established at the time of installation by comparing the speed indicated by the system with a calibrated detection device. The system is configured to an accuracy of +/- 1 MPH of the calibrated detection device reading. The term "calibration" is often used inappropriately in this situation. There are no adjustments made once the initial setup is accomplished, and the only way to change the way the system detects vehicle speed is by changing one of the two constants involved (#1 the distance between the two sensors, and/or #2 the way time is measured by the computer).
A variety of devices are used to verify accuracy and include but are not limited to:
- Vehicle speed test and verification
- Radar detection systems
- Certified speedometers
- Laser speed detection systems
The city's vendor conducts verification of system accuracy routinely for each speed certified location to ensure proper equipment operation. The routine inspections referenced are also conducted when maintenance repairs are performed. In order to put a repaired system back in operation a systems check is performed, and if the indications of improper speed exist, a speed verification check is performed as part of that inspection. These indications include but are not limited to:
- Visible damage to the sensors
- Excessive detection "abortions" due to failed speed tolerance checks
The system performs a speed tolerance test for each detection and ensures the speeds entering and exiting the detection zone are consistent or the detection aborts the processing of the detection as a violation.
Speed verification checks are performed as a result of the following activities:
- Initial installation and commissioning
- Sensor replacement
- Sensor cabling or connector replacement
- Detection system replacement
- During routine inspections for proper system operation